There have been many efforts to develop easily opened containers or easy open containers as they are generally referred to by those familiar with the art. One easy open container developed for use with pressurized liquids such as beer and carbonated beverages employs what is generally referred to as a "pull tab" in which a ring is attached to a severable tab provided in the container's lid. The tab is defined and made severable by a score line provided in the surface of the lid. To open the container, a user lifts or pulls up on the ring which causes the tab to sever from the lid about the score line defining the tab. This tab has been largely replaced by what is referred to today as the "retained tab" primarily due to environmental and safety concerns associated with the pull tab's disposal.
The "retained tab" solved the aforementioned disposal problems since it remains or is retained on the can lid after the can is opened. There are essentially two general types of retained tabs, the first being the push-in or pop-in type and the second being the more commercially successful lever ring type. The lever ring type employs a ring like lever which is attached to a severable tab at the ring-like lever's midsection. The tab is defined and made severable by a score line except for the tab's hinge portion which remains generally unscored and integral with the can lid. To open the can, a user lifts up on one end of the ring-like lever which causes the other end of the lever to press down upon the tab. This action severs the tab about its score line and inwardly displaces the tab into the can's interior about the tab's integral hinge portion. The hinge portion remains integrally connected to the tab after the tab has been severed from the lid and inwardly depressed. As such, the tab is retained on the lid, hence the term "retained tab."
The aforementioned integral hinge concept is also employed to retain the tab on the above mentioned pop-in type container lid. The pop-in tab is similar to the ring-like lever tab but it does not employ a lever to press down upon the tab. Instead, the user presses his finger directly down upon the tab to open the can. This design generally requires that the user apply a relatively significant amount of force against the tab in order to shear at the score line and sever the tab from the lid. Users of the pop-in tab also often cut their fingers on the sharp edge of the lid's opening which becomes exposed as the tab is inwardly depressed into the container.
Another type of retained tab developed is manufactured with the tab severed from the lid except for the tab's integral hinge portion. This tab is also expanded or flattened during manufacturing so as to be overlapped by the can's lid and the tab is sealed to the lid by a sealant applied on the lid's underside. An example of this type of tab is described in U. S. Pat. No. 4,128,186 to Gane. In addition to being severed from and overlapped by the can's lid, the tab disclosed in Gane is provided with primary and secondary sections. The primary and secondary sections are integrally connected by a selectively weakened hinge portion that runs substantially fully across the tab. Sealant also covers the underside of the can's lid to provide a seal between the lid and the respective tab sections. Upon the application of force, the weakened hinge bends or collapses inwardly so as to fracture the sealant having been applied on the lid's underside at the respective ends of the weakened hinge. This fracturing initiates separation of the tab from the lid and also vents excess pressure having built up in the container.
While the overlapped type push-in container lids of Gane and others similar to it undoubtedly work as intended, overlapped configurations are somewhat expensive to manufacture since additional machining steps are required to produce the overlapped configuration and flattened tab. In addition, the overlap creates a dirt collecting sharp cornered recess which is difficult to clean before opening. Moreover, such containers tend to leak since in the absence of pressure provided by the can's contents only the adhesiveness of the sealant holds the tab up against the lid.